The present invention relates to an audio signal editing cross fader used for editing audio signals and the like.
There have been conventional cross faders used in a mixer for editing audio signals comprising a program (PGM) bus including signal lines of the audio signals of a plurality of channels and a preset (PST) bus including signal lines of the audio signals of a plurality of channels. A term "cross fader" used herein means an apparatus for adjusting (fading in and out the levels of signals so that, previous sound is superposed on and gradually changed to, subsequent sound before and after an editing point when the audio sounds and the like are edited. An audio signal before the editing point is a signal on the program (PGM) bus. An audio signal after the editing point is the signal on the preset (PST) bus.
For example, as shown in FIG. 3, selecting and indicating switches 101 through 106, 111 through 116 which are connected to signal lines of a plurality of channels (for example, 6 channels ch1 through ch6) and a fader 121 which achieves, fade-in or fade-out, of audio signals by moving an operation knob 122 is a direction of an arrow S (i.e., a vertical direction) are disposed on a control panel of the conventional cross fader 120.
That is, the selecting and indicating switches 101 through 106 are adapted to select a channel to be programmed by turning on, that is, a channel to be faded out before an editing point. The selecting and indicating switches 111 through 116 are adapted to select a channel to be preset by turning on, that is, a channel to be faded in after the editing point. Each of selecting and indicating switches 101 through 106, 111 through 116 glows to indicate which channel is selected when it is turned on. As shown in FIG. 4, the fader 121 fades out the audio signal of a program (PGM) channel according to a curve F.sub.OUT in FIG. 4 when the operation knob 122 is moved, for example, from the upper end to the lower end and fades in the audio signal of a preset channel according to a curve F.sub.IN in FIG. 4 when the knob 122 is moved, for example, from the lower end to the upper end.
Referring now to FIG. 5, there is shown the schematic structure of a mixer using a usual master fader which performs no cross fading. In FIG. 5, audio signals of channels ch1 through ch6 are supplied to input terminals 131 through 136, respectively. The signals are fed to selecting and indicating switches 151 through 156 via buffer amplifiers 141 through 146, respectively. The switches 151 through 156 are connected with a program bus PB, which is in turn connected with a master fader 160. Accordingly, when any one (or more) of the selecting and indicating switches 151 through 156 is turned on, the signal of the channel selected by turning on is fed to the master fader 160, at which the level of the signal is adjusted and the level adjusted signal is outputted from an output terminal 170.
In the above mentioned conventional cross fader 120, positions of a program bus and a preset bus which are turned on are changed by the vertical movement of the operation knob 122. This is, the indications of the selecting and indicating switches indicating which of the channels which are programmed and preset are changed depending upon the vertical movement of the operation knob 122.
For example, when the channels ch2 and ch4 are in program and preset modes, respectively, both the selecting and indicating switch 102 corresponding to the programmed channel ch2 and the selecting and indicating switch 114 corresponding to the preset channel ch4 light. Movement of the knob 122 to the upper end causes the audio signals of the channels ch2 and ch4 to be faded out and in, respectively. At this time, since the signal of the channel ch2 which has been programmed is faded out, the channel ch2 is brought into a preset mode. Since the signal of the channel ch4 which has been preset is faded in, the channel ch4 is brought into a program mode (refer to FIG. 4). Accordingly, the selecting and indicating switch 102 which indicates a program mode of the channel ch2 fails to light while the selecting and indicating switch 112 which indicates a present mode of the channel ch2 lights. Simultaneously, the selecting and indicating switch which indicates a preset mode of the channel ch4 fails to light while the selecting and indicating switch 104 which indicates a program mode of the channel ch4 lights.
Such changes in program and preset modes are not so troublesome when, for example, video switcher is used since only one source is selected. However, channels to be switched are plural in a switcher which selects (mixes) a plurality of source (audio signals) like a mixer which processes audio signals. Accordingly, change in positions of lighting plural switches due to the above mentioned cross fading operation is very troublesome for an operator of the mixer. That is, since the program and preset buses are relevant to so-called assignment switches in an usual mixer and turning on (lighting) of the assignment switches change by the cross fader, the change in positions of lighting switches are troublesome. Movement of the operation knob of the cross fader in either direction causes a resultant signal to become a faded-in programmed signal. Therefore, the conventional cross fader is very troublesome for users which use a mixer including an usual master fader. The users who are inexperienced in operating such a cross fader may mistake channels which are in program or preset modes, resulting in errors of operation.
Therefore, the present invention was proposed under the above mentioned circumstances.
It is an object to provide a cross fader for editing audio signals which gives, good feeling of use and may reduce errors of operation.